Resistance seam welding is widely used for joining metallic members. For example, resistance seam welding is utilized in welding gas turbine engine recuperators. A typical recuperator may have several thousand feet of resistance welded seams. One problem which affects the quality of the overall weld is related to sporadic increases in electrical resistance at the curved rotating electrical contact surfaces inside one or both of the welding heads of the welding machine. Such sporadic increases in electrical resistance have been attributed to poor mating surface contact related to machining errors. That is, the machining of the curved electrical contact surfaces to the dimensions required for intimate contact between the curved electrical contact surfaces is difficult to achieve. Sporadic increases in electrical resistance have also been attributed to nonuniform wear of the electrical contact surfaces during the welding operation itself. Sporadic increases in electrical resistance have also been attributed to an inherent inability of the welding head to accommodate surface irregularities of the rotating electrical contact surfaces by increasing the contact pressure of these electrical contact surfaces in the welding head. That is, these rotating electrical contact surfaces do not suitably rotate if the contact pressure is increased to too great a level.
As can be appreciated, due to the difficulty in inspection of the completed complex workpiece, such as a gas turbine engine recuperator, it is important that the welding operation be performed in a manner which substantially reduces the possibility of the formation of a defective weld.